Electrical apparatus



June 19, 1962 M. MORISUYE I 3,040,281

ELECTRICAL APPARATUS Filed June 25, 1958 Fi 3. wlrmzssss: g INVENTOR Mosonobu Morisuye M i. mc/AA fajm United States Patent 3,04-tl,281 ELECTRICAL APPARATUS Masanobu Morisuye, Sharon, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed June 23, 1958, Ser. No. 743,748 11 Claims. (Cl. 336-206) This invention relates to electrical inductive apparatus, such as transformers, and more particularly to the insulation structure of such apparatus.

It is well known that where alternating voltages are applied to an insulation structure in an electrical inductive apparatus, such as transformers, which includes both solid insulation and layers of a fluid dielectric such as insulating oil, the electrical stress divides inversely in proportion to the dielectric constant of the different insulating materials. Since the dielectric constant of a solid insulation is usually higher than that of a conventional insulating oil, the oil spaces between the parts being insulated must be sufliciently large enough to keep the electrical stresses below the corona strength of the insulating oil. In certain types of transformers, spaces are commonly provided between the insulated parts of the transformer for cooling ducts through which the insulating oil may circulate. The spacing of such cooling ducts must be suflicient therefore to reduce the electrical stress imposed on the insulating oil below the corona strength of the oil to prevent insulation failure. The effect of the presence of the cooling ducts in a transformer is to increase the size and weight of the transformer. In certain types of electrical induction apparatus, such as potential transformers Where cooling is of only minor importance, it is therefore advantageous to provide an insulation structure which substantially eliminates cooling ducts and reduces the size and weight of the transformer and also more effectively utilizes the inherent dielectric strength of the insulating material employed in such a structure.

It is an object of this invention to provide a new and improved electrical induction apparatus, such as a transformer.

Another object of this invention is to provide an electrical inductive apparatus, such as a transformer, having a smaller size and weight.

A further object of this invention is to provide an electrical induction apparatus including a magnetic core and windings in which insulation is packed substantially solidly between the windings and between the windings and the core, at least a part of said solid insulation being impregnated with a fluid dielectric.

Other objects of this invention will, in part, be obvious and will, in part, appear hereinafter.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in "connection with the accompanying drawing, in which:

FIG. 1 is a simplified outline drawing of a transformer embodying the teachings of this invention;

FIG. 2 is a top plan view partly in section of the core and coil assembly of the transformer shown in FIG. 1; and

FIG. 3 is a partial side elevational view in section of one of the windings of the transformer shown in FIG. 1 illustrating the method of assembly of the windings.

Referring now to the drawing and FIG. 1 in particular, there is illustrated a simplified outline drawing of an electrical induction apparatus, specifically the transformer illustrating the general arrangement of the parts included in the transformer 10. The transformer 10 includes a first or low voltage winding 20, a second or high voltage winding 40, a magnetic core 30 on which said windings are "ice disposed which make up a core and coil assembly which is disposed in a casing 50. In addition, the transformer 10 includes the bushings 92 and 96 and the terminal connector structure 94 through which external connections are made to the second winding 40. The casing 50 also includes means (not shown in detail) for mounting the bushings 92 and 96.

Referring now to FIG. 2, there is illustrated the core and coil assembly 60 of the transformer 10 which includes the magnetic core 30, a first winding 20, and a second winding 40. The magnetic core 30 includes first and second outer leg members 32 and 36 and a middle or winding leg member 34 which form two windows in the magnetic core 30. The magnetic core 30 is illustrated as being of the shell form type in which the windings 20 and 40 are disposed on the winding leg member 34.

In particular, the first winding 20 includes a plurality of cylindrically wound turns of the conducting material 26, the turns of the winding 20 being insulated from each other by solid insulation in a suitable form such as tape made from cotton or paper or enamel coating or combina tions of such materials. The turns of the first winding 20 are cylindrically wound on an insulating tube or supporting member 56 which is formed from a suitable insulating material, such as a resin impregnated paper laminate. Since the over-all width of the first winding 20' is less than the width of the second winding 40, the insulating spacing collars 52 are provided adjacent to the ends of the first winding 20 in order to keep the active winding space of the first winding 20 approximately equal to that of the second winding 40.

In detail, the second winding 40 includes a plurality of disk-type or pancake-type coils '70 each having a plurality of turns of the conducting material 74. The turns of the disk-type coils 70 are insulated from each other by solid insulation in a suitable form. For example, the conducting material 74 may be coated with an insulating enamel, or coated with an insulating enamel and covered with paper or cotton. The disktype coils 70 are also insulated from each other by the coil-to-coil insulation 72 which may be of any suitable form, such as tape. In order to increase the surge capacity of the pancake coils 70, each of the coils 70 is provided with an inner static ring 44 and an outer static ring 55 which are each wrapped with a suitable solid insulating material 45 and 57, respectively. In addition, the disk-type coil 70 located at the left end of the magnetic core 30 has one or two static plates 42, as required in a particular application. When two static plates are used, they are disposed on each side of the pancake coil 70. The static plates 42 are each covered with a suitable sol-id insulation 76 which may be in the form of an insulating tape. In addition, the first pancake coil 70 at the left end of the magnetic core 30 and the associated static plate or plates 42 are also provided with or wrapped in an additional layer of solid insulation 88.

The insulation structure between the first and second windings 20 and 40' and between said windings and the magnetic core '30 will now be described. In general, the space between the first and second windings 20 and 40 and between said windings and the core 30 is substantially filled with solid insulation, including cellulosic insulation. At least a part of the solid insulation provided is impregnated or permeated with a suitable fluid dielectric, such as a conventional insulating oil.

In particular, a layer of cellulosic insulation 54 is pro vided between the first winding 20 and the second winding 40 which in this case is concentrically disposed around theoutside of the first winding 20. In addition, a layer of flexible cellulosic of fibrous insulation 68, such as crepe paper, having an extending portion 67 is disposed between the first winding 20 and the second winding 40.

There is also provided a second layer of flexible cellulosic insulation 62, having the extending portions 6 1 and 63 at each end, which is disposed between the first winding and the second winding 40. The extending portions 61 and 63 of the second layer of cellulosic insulation 62 are pulled back over the outside of the second winding 40 at both ends of the second winding 40. The extending portion 67 of the first layer of cellulosic insulation 68- is pulled back over the outside of the extending portion 61 of the second layer 62 and the outside of the second winding 40 at the left end of the second winding 40 for reasons which will be explained hereinafter.

In an application requiring additional insulation between the second winding40 and the magnetic core the insulating washers 82 and 84 are provided at the left and right ends of the second winding 40, respectively. The insulating washers 82 and 84 are formed from a suitable solid insulating material, such as pressboard. In addi- 7 tion, the space between the second winding and the magnetic core 30 and the space between the ends of the extending portions of the insulation layers 62 and 68 are packed substantially solidly with the solid insulation 75 which may be of any suitable insulating material, such as crepe paper. A final layer 66 of a suitable solid insulation, such as crepe paper, may be provided around the winding 40 to provide additional insulation between the latter winding and the magnetic core 30.

The ends of the first winding 20 are brought out to the external terminals 22 and 24 by the lead conductors 23 and 25, respectively. One end of the second or high voltage winding 40 is connected to the line terminal 12 by the line lead conductor 13. The other end of the second winding 4% is connected to a ground connection as indicated at 14 by the neutral lead conductor 15. The transformer 10, as shown in FIGS. 1 and 2, is illustrated as being adapted specifically for connection to an electrical power system (not shown) having a grounded neutral. The terminal 12 of the transformer core and coil assembly would be connected to the line conductor of such a system, and the neutral lead of the second Winding 40 of the transformer core and coil assembly 60 would be connected to the neutral conductor of such a system through the bushing 96 shown in FIG. 1. Since the insulation required adjacent to the line lead 13 of the second winding 40 shown in FIG. 2 must be insulated to a greater degree than the neutral side of the second winding 40 adjacent to the neutral lead 15, the extending portions 61 and 67 of the first and second layers of cellulosic insulation 62 and 68, respectively, are both pulled back over the second winding 40 adjacent to the line lead 13. In addition, the disk-type coil connected to the line lead 13 at the left end of the second winding 40 is provided with the static plate or plates 42 to supplement the dielectric strength of the disk-type coils 70 nearest to the line lead 13 where the stress due to impulse voltage is greatest. It is to be understood that a transformer embodying the teachings of this invention may be provided with both ends of the second winding 40 having substantially the same level of insulation for connection from line to line of an electrical power system instead of from line to ground of such a system. It is to be noted that the various disk-type coils 70 which make up the second winding 40 are all interconnected by suitable connecting leads (not shown) between the line lead 13 and the neutral lead 15.

Referring now to FIG. 3, there is illustrated the manner in which the diflerent layers of cellulosic insulation are assembled around the first winding 20. In particular, after the turns of the conducting material 26 of the first winding 20 have been cylindrically wound on the insulating tube 56, and the insulating spacing collars 52 have been assembled at each end of the turns of the first winding 20, a first layer of cellulosic insulation 54 is provided over the turns of the winding 20* and the associated spacing collars 52. Next the layer of cellulosic insulation 68 is provided around the low voltage winding 20 by wrapping a plurality of turns of a suitable insulating material, such as crepe paper in the form of sheets, having an extending portion 67 at the left end of the first winding 20. Then a layer of cellulosic insulation 62, having the extending portions 61 and 63 at the left and right ends of the winding 20 respectively, is formed by wrapping a second plurality of turns of a suitable insulating material, such as crepe paper in the form of sheets. The second winding 40, which includes the plurality of disk-type coils 70, is assembled separately and is then assembled or disposed concentrically around or outside the first winding 20. The extending portions or" the layers of cellulosic insulation 62 and 68 are then pulled back over the adjacent end of the outside of the second winding 40 as shown in FIG. 2. The insulating material used to form the layers of cellulosic insulation 62 and 68, the extending portions of which are pulled back over or folded back over the second winding 49, are preferably of the flexible type which can be conveniently pulled or stretched during the assembling of the first and the second windings 20 and 40, respectively shown in FIG. 2. It is to be understood that other types of cellulosic of fibrous insulation, which are permeable or porous to allow impregnation by a fluid dielectric, may be employed similarly where the dielectric strength of the impregnated insulation is greater than that of the fluid dielectric alone.

In summary the construction disclosed includes a magnetic core on which one or more electrical windings are disposed with solid insulation, including cellulosic or fibrous insulation, packed substantially solidly around and between the turns and the coils of the windings, between the respective windings, and between the windings and the core. The space between the turns and the coils of the windings, between the respective windings, and between the windings and the core is therefore substantially filled with solid insulation, including cellulosic insulation, with at least a part of the solid insulation being impregnated with a fluid dielectric such as insulating oil. This results in a substantially uniform stressing of the solid insulation and a more eficient use of the insulation in an electrical inductive apparatus, such as a transformer. The fluid dielectric spaces in the insulation structure between the windings and between the windings and the magnetic core of the described apparatus are therefore substantially eliminated to prevent insulation failure of the fluid dielectric alone which would otherwise form a weak link in the insulation structure. permits smaller clearances between the parts of an apparatus insulated from each other and permits closer electrical coupling between the windings of an electrical apparatus as disclosed.

It is to be understood that a transformer for an electrical inductive apparatus as disclosed could include three or more windings or two windings, including a winding having several portions or groups disposed on opposite sides of the first winding. The latter arrangement could be used to provide an interleaved construction for better electrical coupling or to provide a divided or multiple section winding on a transformer. For example, a transformer could include a first winding similar to the winding 46 shown in FIG. 2 and a second winding having two portions similar to the winding 20 shown in FIG. 2 disposed on the inside and on the outside of the winding 40, respectively, in a particular application. As illustrated, the cylindrically wound winding 20 and the disktype coils 70 of the winding 40 are illustrated as having a substantially circular shape in cross section. It is to be understood that the windings 20 and 40 may have rectangular or other shapes in cross section in a transformer as disclosed. It is also to be understood that the static plates 42 and the static rings 44 and 55 provide as part of the second winding 40 to protect the winding 40 against voltage surges and may take other forms or shapes in a particular application. 7

The apparatus embodying the teachings of this inven- The construction thus disclosed tion has several advantages. For example, the required size and weight of an electric apparatus, such as a transformer, as disclosed is reduced because of the more eflicient use of solid insulation including cellulosic insulation to thereby reduce the necessary clearance between the insulated parts of the transformer. The closer coupling between the windings of such apparatus also reduces the impedance of the transformer and in the case of an instrument type transformer reduces the magnitude of variation in the accuracy of the transformer from zero to its rated burden rating. The reduced clearances between the windings and between the windings and the core of the transformer as disclosed improves the space factor of such apparatus to thereby reduce the required amount of magnetic material in the core structure and the conducting material required in the windings. It is assumed that the core and coil assembly of the transformer as disclosed is processed following assembly by drying and impregnating the assembly with a suitable fluid dielectric, such as insulating oil to obtain the advantages listed.

Since numerous changes may be made in the above described apparatus and different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all the matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. A transformer comprising, a magnetic core including a winding leg member, a first winding including a plurality of turns disposed around said winding leg member, a second winding including a plurality of disk-type coils disposed in side by side relation with one another and each comprising a plurality of turns disposed about said first winding, solid insulating material including at least one layer of flexible cellulosic insulating sheet material disposed between said windings and pulled back over the outside of said second winding, said solid insulating material being packed to substantially fill the space between the turns of said windings, between said first and second windings and between said windings and said core, and fluid dielectric impregnating at least a part of said solid insulating material.

2. A transformer comprising, a magnetic core, a first insulated winding including a plurality of turns of conducting material cylindrically wound on a portion of said core, a second winding including a plurality of disk-type coils disposed in side by side relation with one another, each of said coils having a plurality of turns of conducting material and being concentrically disposed about said first winding, solid insulating material including a layer of flexible cellulosic insulating sheet material wrapped around said first winding with the ends of said layer pulled back over the outside of said second winding, said solid insulating material being disposed to substantially fill the space between the turns of said windings and the space between said first and second windings and between said windings and said core, and dielectric fluid permeating at least part of said solid insulation.

3. An electrical inductive apparatus comprising, a magnetic core, an inner winding comprising a plurality of cylindrically wound turns of conducting material disposed about a portion of said core, an outer winding comprising a plurality of disk-type coils each comprising a plurality of turns of conducting material, said coils being disposed in side by side relationship with one another, said outer winding being concentrically disposed around said inner winding, solid insulation including at least first and second layers of flexible cellulosic sheet insulation wrapped around said inner winding between said inner and outer windings, said solid insulation being packed to substantially fill the space around the turns and coils of said windings, between said inner and outer windings, and between said windings and said core, both ends of said first layer of cellulosic insulation being pulled back over the outside of said outer winding and one end of said second layer of cellulosic insulation being pulled back over the outside of said outer winding, and a fluid dielectric impregnating at least a portion of said solid insulation.

4. A transformer comprising, a magnetic core including a winding leg member, a first winding including a plurality of cylindrically wound turns of conducting material disposed on said winding leg member, a second winding including a line lead, a neutral lead and a plurality of insulated pancake-type coils each having a plurality of turns of conducting material, said coils being disposed in side by side relationship with one another, said second winding being concentrically disposed adjacent to said first winding, solid insulation including first and second layers of flexible, fibrous sheet insulation wrapped around said first winding between said first and second windings, said solid insulation being disposed to substantially fill the space between the turns and coils of said windings, between said first and second windings and between said windings and said core, both ends of said first layer of fibrous insulation being pulled back over the outside of said second winding and one end of said second layer of fibrous insulation being pulled back over the outside of said second winding adjacent to said line lead, and a fluid dielectric impregnating at least a part of said solid insulation.

5. A transformer comprising, a magnetic core including a winding leg member, a first winding including a plurality of cylindrically wound turns of conducting material disposed on said winding leg member, a second winding including a line lead, a neutral lead and a plurality of insulated pancake-type coils each having a plurality of turns of conducting material, said coils being stacked substantially parallel to the axis of said leg member, said second winding being concentrically disposed adjacent to said first winding, solid insulation including first and second layers of crepe paper insulation wrapped around said first winding between said first and second windings, said solid insulation being disposed to substantially fill the space between the turns and coils of said windings, between said first and second windings and between said windings and said core, both ends of said first layer of crepe paper insulation being pulled back over the outside of said second winding and one end of said second layer of crepe paper insulation being pulled back over the outside of said second winding adjacent to said line lead, and a fluid dielectric impregnating at least a part of said solid insulation.

6. A transformer comprising, a magnetic core including a winding leg member, a first winding including a plurality of cylindrically wound turns of conducting material disposed on said winding legmember, a second winding including a plurality of disk-type coils each having a plurality of turns of conducting material concentrically disposed around said first winding, said coils being stacked substantially parallel to the axis of said leg member, solid insulation including a layer of flexible cellulosic sheet insulation having extending portions at each end wrapped around said first winding, said solid insulation being packed to substantially fill the space between the turns and coils of said windings, between said first and second windings and between said windings and said core, the extending portions of said layer of cellulosic insulation being pulled back over the outside of said second winding, and fluid dielectric impregnating at least a part of said solid insulation.

7. A transformer comprising, a magnetic core including a winding leg member, a first winding including a plurality of cylindrically wound turns of conducting material disposed on said winding leg member, a second winding including a plurality of pancake-type coils each having a plurality of turns of conducting material concentn'cally disposed around said first winding, said coils being disposed in side by side relation with one another along the axis of said leg member, solid insulation including first and second layers of flexible fibrous insulation wrapped around said first winding, said solid insulation being disposed to substantially fill the space between the turns and coils of said windings, the space between said first and second windings and the space between said windings and said core, said first layer of fibrous insulation having extending portions pulled back over the outside of said second winding, said second layer of fibrous insulation having an extending portion at one end pulled back over the outside of said second winding at one end thereof, and fluid dielectric impregnating at least a part of said solid insulation.

8. A transformer comprising, a magnetic core including a winding leg member, a first winding including a plurality of turns disposed around said winding leg member, a second winding including a plurality of disk-type coils each comprising a plurality of turns disposed about said first Win-ding, said coils being stacked in side by side relation with one another substantially parallel to the axis of said leg member, solid insulating material including at least one layer of flexible cellulosic insulating sheet material disposed between said windings and pulled back over the outside of said second winding, said solid insulating material being packed to substantially fill the space between the turns of said windings between said first and second windings and between said windings and said core, and fluid dielectric impregnating at least a part of said solid insulating material.

9. A transformer comprising, a magnetic core, a first insulated winding including a plurality of turns of conductin-g material cylindrically wound on a portion of said core, a second winding including a plurality of disk-type coils each having a plurality of turns of conducting material and concentrically disposed about said first winding, said coils being assembled in side by side relation with one another longitudinally of the axis of said portion of said core, solid insulating material including a layer comprising a plurality of turns of flexible cellulosic insulating sheet material wrapped around said first winding with the ends of said layer pulled back over the outside of said second winding, said solid insulating material being disposed to substantially fill the space between the turns of said windings and the space between said first and second windings and between said windings and said core, and dielectric fluid permeating at least part of said solid insulation.

10. In an electrical inductive apparatus comprising, a magnetic core, an inner winding comprising a plurality of cylindrically wound turns of conducting mate-rial disposed about a portion of said core, an outer winding comprising a plurality of disk-type coils each comprising a plurality of turns of conducting material, said coils being disposed in side by side relationship with one another, said outer winding being concentrically disposed around said inner winding, solid insulation including at least first and second layers each comprising a plurality of turns of flexible cellulosic sheet insulation wrapped around said inner winding between said inner and outer windings, said solid insulation being packed to substantially fill the space around the turns and coils of said windings, between said inner and outer windings, and between said windings and said core, both ends of said first layer of cellulosic insulation being pulled back over the outside of said outer winding and one end of said second layer of cellulosic insulation being pulled back over the outside of said outer winding, and a fluid dielectric impregnating at least a portion of said solid insulation.

11. A transformer comprising, a magnetic core including a winding leg member, a first winding including a plurality of cylindrically wound turns of conducting material disposed on said winding leg member, a second winding including a plurality of pancake-type coils each having a plurality of turns of conducting material concentrically disposed around said first winding, said coils being disposed in side by side relation with one another along the axis of said leg member, solid insulation including first and second layers each comprising a plurality of turns of flexible fibrous sheet insulation wrapped around said first winding, said solid insulation being disposed to substantially fill the space between the turns and coils of said windings, the space between said first and second windings and the space between said windings and said core, said first layer of fibrous insulation having extending portions pulled back over the outside of said second winding, said second layer of fibrous insulation having an extending portion at one end pulled back over the outside of said second winding at one end thereof, and fluid dielectric impregnating at least a part of said solid insulation.

References Cited in the file of this patent UNITED STATES PATENTS 1,118,446 ROos Nov. 24, 1914 1,567,797 Frank Dec. 29, 1925 1,862,503 Cadieux June 7, 1932 2,359,544 Camilli Oct. 3, 1944 2,498,238 Berberich et al Feb. 21, 1950 

